Depth gauge and method of treating a depth gauge

ABSTRACT

The present invention relates to a device for determining the correct lengths of standardized components of a dental implant system in situ in the oral cavity. The device comprises an elongate gauge body (1, 2) being provided with circumferential dark bands (10, 18, 19, 20, 21) located at predetermined distances from each other and having predetermined widths, the areas between said darker bands having a pronouncedly lighter colour, each boundary line between lighter and darker bands corresponding to one specific, standardized component.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a device for determining the correctlengths in situ of standardized components of a dental implant system tobe used in the oral cavity, more particularly to a device for measuringthe depth of holes drilled or bored into the jaw bone for the subsequentinsertion of fixtures for dental prostheses as well as to a device forfacilitating the correct choice of an abutment for bridging the softtissue around the hole and to be mounted on a fixture inserted into saidhole. The invention also relates to a method for treating said device.

BACKGROUND TO THE INVENTION

A system for dental prostheses commonly used today comprises a more orless cylindrical fixture which is inserted into a bore-hole drilled intothe uncovered jawbone. The system further comprises a conical abutmentor pillar, intended to carry the prosthesis, which is to be attached tothe fixture, thus bridging the layer of soft tissue covering thejawbone. The abutment is complementary to a conical bore in the top ofthe fixture. The abutment is provided in several standard lengths inorder to allow the correct choice of abutment in dependence of thethickness of the soft tissue around the implant site after implantation.

The choice of the correct abutment is very important inter alia foraesthetic reasons. This choice may however be time-consuming and mayalso be troublesome for the patient. There thus is a need for a toolwhich facilitates the choice of abutment and which is simple to use andto read in the environment of the oral cavity.

It may also be difficult to chose the correct fixture which is to fitinto the hole drilled into the bone. It is important that the fixture isflush with the uncovered bone tissue or slightly below the edge of thebore-hole.

Generally, when implants are fitted into bone tissue, different kinds ofmetallic surgical tools are used to prepare the site in the tissue wherethe implant is to be located. These tools normally are made of carbonsteel (normally in disposable tools) or surgical grade stainless steelor titanium or titanium alloys (normally in non-disposable tools).

In some cases it may be advantageous if at least the surface of thetools are covered with a material which is more biocompatible than thematerial in the tool even if the tool is not to remain in the bonetissue for a long period of time.

If the tool is not of an inert material as regards the chemicalenvironment prevalent in bone tissue and blood, some slightcontaminations may affect the sides of the bore hole. These contaminantsmight possibly affect the so-called osseointegration process which seemsto be very important in connection with bone implants and which seems tobe sensitive in respect of contaminants.

Another prerequisite for a good osseointegration is a good, stable fitbetween bone tissue and implants, the osseointegration being dependenton a close contact between bone tissue and implant surface. When abore-hole for an implant has been drilled, it therefore is importantthat the length of the bore-hole corresponds as closely as possible tothe length of the implant chosen.

If the bore-hole in the jaw-bone should happen to be to shallow for theimplant which has been deemed to be suitable in a specific location inthe oral cavity, it is important to be able to ascertain this inadvance, because of the trauma to the bone tissue that might be theconsequence of the implant first being screwed into the bore-hole andthen being unscrewed again. If it is vital that the implant chosenactually is used in this specific location, the threads in the bore alsomight be damaged by the necessary, additional drilling procedure.

BRIEF DESCRIPTION OF THE INVENTION CONCEPT

The above object is achieved in that said device comprises an elongatebody being provided with circumferential dark bands located atpre-determined distances from each other and having pre-determinedwidths, the areas between said darker bands having a pronouncedlylighter colour, each boundary line between lighter and darker bandscorresponding to one specific, standardized component.

In a preferred embodiment said darker bands have been etched, by meansof a laser beam, in a layer of brightly coloured titanium nitridecovering the surface of the device, or, in case the device is made bytitanium or titanium alloy, the bands may be etched directly in thetitanium surface.

Further advantageous embodiments of the invention are set forth in thedependent claims.

BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

FIG. 1 illustrates one side of preferred embodiment of a combined devicein accordance with the invention,

FIG. 2 shows the other side of the device in FIG. 1,

FIG. 3 illustrates a preferred embodiment of the device for determiningthe length of an abutment to be used,

FIG. 4 shows the preferred embodiment of a device for determining thedepth of a bore-hole in the jaw-bone,

FIG. 5 a detail of the device in FIG. 4.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

As can be seen in FIGS. 1 and 2, a preferred embodiment of the inventioncomprises a body 1 or abutment gauge for determining the correct lengthof an abutment, a body 2 or fixture gauge for determining the depth of ahole drilled into the jawbone and a handle 3 joining the two gaugebodies. The gauges are angled relative to the handle in order tofacilitate the use of the tool or device in the oral cavity. FIG. 1further illustrates that one side of the handle is provided withnumerals 4 indicating the lengths of the different standard fixtures andFIG. 2 illustrates the markings on the other side of the handlecorresponding to the different sizes of abutments.

FIGS. 3 and 7 show the construction and use of the abutment gauge inmore detail. As can be seen in FIG. 3, the lower part 5 of the abutmentgauge has a conical or tapering shape which corresponds exactly to theshape of the lower part 6 of an abutment 7 (FIG. 7). The upper part ofthe abutment gauge is provided with circumferential dark bands 10. Thebands 10 are spaced equidistantly over the body of the gauge. Asindicated by the chain of measurements 11, the distance between thebands and the width of the bands in this particular case is 1.5 mm. Eachboundary line will correspond to a specific length of the cylindricalpart 9 of the abutments 7.

The free end of the lower part 5 may be provided with a relativelyshort, cylindrical projection having a rounded end which preferably ishemispherical. The cylindrical part of the projection is complementaryto a cylindrical continuation of the conical bore in the fixture 8 andwill by these means ensure a correct orientation of the lower part 5when this part is inserted into the fixture. The rounded part of theprojection will facilitate the insertion of the abutment gauge into theconical bore of the fixture.

As can be seen in FIG. 7, the conical part of the abutment gauge 1 isinserted in the fixture 8, which is located in a bore-hole in the bonetissue of the jaw-bone 12. The thickness of the soft tissue covering thejaw-bone 12 can be measured against an adjacent boundary line between adark band and a light band, allowing the correct choice of an abutmentfor this particular fixture. The titanium nitride has a bright yellowcolour and the darker bands are almost black, and consequently a verydistinct level indication is given at each boundary line between darkerbands and lighter areas. This level indication will be very easy to readin the conditions prevalent in the oral cavity regarding for instancelight and available space. It should be noted that the contrast betweenthe darker bands and the lighter bands on a titanium gauge also issufficient to give the above, distinct level indication.

The details of the fixture gauge and its use are illustrated in FIGS. 4,5 and 6. As indicated in FIG. 4, the fixture gauge comprises anelongate, conically tapering rod 15 which at its free end is providedwith a transversely oriented plate or button 16 which is seen in moredetail in FIG. 5.

As indicated by means of the chain of measurements 17, a dark band 18having a width of 1 mm is located at a distance of 8 mm from the tip ofthe rod 2. Each following dark band 19, 20, 21 is separated from theadjacent band by means of a space having a width of exactly 2 mm. Again,a very distinct level indication is given at each boundary line betweendarker bands and lighter areas. The button 16 also has a definedthickness, in this case 1 mm.

The fixture gauge is inserted into an uncovered bore-hole 14 in thejaw-bone 12, the button 16 being slid along the side-wall of the holeuntil it reaches the corner formed by the side-wall and the bottom ofthe hole (the bottom of the hole normally being slightly conical due tothe shape of the drills normally used) and the depth of the hole is readagainst the bands of the gauge, allowing the correct fixture to bechosen. If there should be any doubt whether the corner has beenreached, this can be checked by moving the gauge to the middle of thehole. The difference in depth should not be more than maximally 0.4 mmwith regard to the specific fixture diameters used in the above system.

The button is particularly important when holes in the upper jaw aremeasured. These holes may some times extend into the sinusoidal cavity,and in this case it is important to measure the thickness of the bonetissue. This may be done by hooking the button on the edge of the holein the cavity and reading the thickness of the bone tissue at the edgeof the hole in the oral cavity against the bands on the rod, taking intoaccount that exactly 1 mm should be subtracted from the measurementobtained due to the thickness of the button.

Bone implants may also be relatively smooth instead of being providedwith threads. This kind of implants may be carefully tapped into placein a borehole in the bone, which bore-hole may have a slightly narrowerdiameter than the implant, by means of a small hammer. However carefullythis is done, there always is a risk that the fixture may be pushed tofar down into the hole if the hole does not exactly correspond to thefixture. The fixture gauge according to the invention thus may beparticularly useful in this case, since it may be difficult to extricatean implant which has been pushed to far down into a hole.

These problems might also arise if the bore-hole is to shallow for theimplant since the act of extrication per se might cause a trauma to thewalls of the bore-hole which might have a deleterious influence on theosseointegration process.

If the surface of the bone into which the fixture is to be inserted isobliquely oriented relative to the longitudinal direction of the hole,the above-mentioned boundarys on the fixture gauge will also serve asindexes on a ruler for measuring the difference in level between theedges of the bore-hole and will consequently be very useful whendetermining how deep the hole has to be in order to house the implantcorrectly in relation to the oblique surface of the bone.

The device according to the invention can be treated by the followingsteps:

a) coating the gauge with a thin layer of titanium nitride (TiN) bymeans of chemical vapour deposition until the drill obtains a brightpermanent colour,

b) etching circumferential bands with pre-determined widths beinglocated at pre-determined distances from each other around the outersurface of the body by means of a laser beam, the bands thus being darkand sharply defined.

In case the gauge is made of titanium or titanium alloys, the darkerbands may be laser-etched directly in the titanium surface. It ishowever also quite within the scope of the invention to cover a gaugemade of titanium or an alloy thereof with TiN and etching the bandstherein.

The use of a laser beam has the advantage that the boundary lines willbe very sharp and well defined and that the contrast between darker andlighter areas will be high.

The etched areas will remain essentially smooth in spite of thetreatment, which ensures that there will be no rough areas on the deviceupon which contaminants easily will adhere.

It should be emphasized that the invention is not limited to theembodiment described above and can be varied in many ways within thescope of the appended claims.

We claim:
 1. A surgical instrument for use in the surgical procedure forimplanting a dental implant system of the type which includes:a fixturecomponent part having a leading end and a trailing end and adapted to beanchored in a jaw bone of a patient by insertion of the leading endthereof into a bore which extends into the jaw bone from a surfacethereof, the fixture component part being a standard fixture componentpart of predetermined length and selected from a set of standard fixturecomponent parts of different predetermined lengths so that on anchorageof the fixture component part in the jaw bone the trailing end isessentially flush with the surface of the jaw bone; and an abutmentcomponent part for bridging a layer of soft tissue which covers thesurface of the jaw bone to couple a dental prosthesis to the fixturecomponent part, the abutment component part having a leading end whichis adapted to be inserted through a surface of the soft tissue layer andto mate with the trailing end of the fixture component part in the jawbone and a trailing end which when the leading end of the abutmentcomponent part mates with the trailing end of the fixture component partprojects from the surface of the soft tissue layer and is adapted tosupport the dental prosthesis, the abutment component part being astandard abutment component part of predetermined length and selectedfrom a set of standard abutment component parts of differentpredetermined lengths so that when the leading end of the abutmentcomponent part mates with the trailing end of the fixture component partessentially only the trailing end of the abutment component part whichsupports the dental prosthesis projects from the surface of the softtissue layer; wherein the surgical instrument comprises:a depth gaugebody having a leading end, a trailing end and an outer peripheralsurface extending between the leading and trailing ends, wherein theleading end of the depth gauge body is a replica of the leading end ofthe abutment component part and adapted to be inserted through thesurface of the soft tissue layer to mate with the trailing end of thefixture component part in the jaw bone, wherein the outer peripheralsurface of the depth gauge body is provided with a series of alternatedark and light colored bands of predetermined widths, the boundary linesbetween adjacent dark and light colored bands representing standardabutment component parts of different predetermined length in the setthereof, and further wherein when the leading end of the depth gaugebody mates with the trailing end of the fixture component part in thejaw bone the depth of the soft tissue layer is able to be determinedfrom the boundary lines which project from the surface of the softtissue layer whereby a standard abutment component part of correctpredetermined length is able to be selected from the set of standardabutment component parts.
 2. An instrument according to claim 1, whereinthe leading end of the depth gauge body is presented by a leadingportion of the outer peripheral surface, wherein the leading portion ofthe outer peripheral surface defines a shape which corresponds to theshape of that portion of the abutment component part which presents theleading end of the abutment component part and wherein the series ofalternate dark and light colored bands is provided on the outerperipheral surface of the depth gauge body which extends between theleading portion and the trailing end.
 3. An instrument according toclaim 1, wherein the depth gauge body is a first depth gauge body,wherein the instrument presents a second depth gauge body having aleading end, a trailing end and an outer peripheral surface extendingbetween the leading and trailing ends, wherein the leading end of thesecond depth gauge is adapted to be inserted into the bore in the jawbone, wherein the outer peripheral surface of the second depth gaugebody is provided with a series of alternate dark and light colored bandsof predetermined widths, the boundary lines between adjacent dark andlight colored bands on the second depth gauge body representing standardfixture component parts of different predetermined length in the setthereof, and further wherein insertion of the leading end of the seconddepth gauge into the bore in the jaw bone enables the depth of the boreto be determined from the boundary lines which project above the surfaceof the jaw bone whereby a standard fixture component part of correctpredetermined length is able to be selected from the set of standardfixture components.
 4. An instrument according to claim 3, wherein theleading end of the second depth gauge body defines a transverselyoriented button or plate.
 5. An instrument according to claim 3, whereinthe outer peripheral surface of each depth gauge body is coated with athin layer of titanium nitride (TiN) and wherein the bands of dark colorare bands of laser etched titanium nitride.
 6. An instrument accordingto claim 3, wherein the trailing ends of the first and second depthgauge bodies are connected to one another by a handle.
 7. A method ofmanufacturing a surgical instrument according to claim 3, the methodincluding the steps of:(i) forming each depth gauge body from a metalselected from the group consisting of surgical grade stainless steel,surgical grade carbon steel, titanium and titanium alloys; (ii) coatingthe outer peripheral surface of each depth gauge body with a thin layerof titanium nitride (TiN) by chemical vapor deposition until the outerperipheral surface of the depth gauge body obtains a permanent brightcolor; and (iii) etching the outer peripheral surface of each depthgauge body with a laser beam so as to produce a plurality of dark bandson the outer peripheral surface of the depth gauge body of predeterminedwidths and spacing.